Lyme Disease – Xenodiagnosis and Chronic Lyme Disease

by lmatthews on April 19, 2012

Fancy having 30 ticks attached to you for five days? Xenodiagnosis could change the face of Lyme disease testing.

In an effort to put to rest any controversy, a study into the xenodiagnosis of Chronic Lyme Disease is underway in the US which involves patients being subjected to tick bites. These uninfected ticks, up to thirty at a time, are allowed to feed on patients treated for Lyme disease before the ticks are tested for the Lyme disease bacteria. Could the tables be turned on ticks? Could they themselves become part of Lyme disease diagnosis?

NIAID Tick Tests

Researchers at the National Institute of Allergy and Infectious Diseases (NIAID) are in the middle of a clinical trial looking at xenodiagnosis in humans. The method has been tested with animals before but this is the first human trial involving ticks feeding on volunteers in the hope of increasing knowledge about Lyme disease. Dr Adrian Marques is leading the study which aims to open up new research directions around post-treatment Lyme disease syndrome, Chronic Lyme disease, and persistent infection with Borrelia.

Patients Keen to be Bitten

The chance to turn the tables on ticks means that the study is not short of volunteers, even though those participating in the trial will have thirty ticks attached to them for several days. The ticks are positioned on the skin under a filter and covered with a dressing to stop them migrating over the four or five day period in which they remain in place. Ticks are thought to take an average of thirty-six hours from first biting a human host to transmit the bacteria, with little risk of infection if they are removed within the first twenty-four hours of being attached. This is different for European and Asian tick species which are thought more likely to carry the Lyme disease bacteria present in the saliva, allowing for faster transmission to their host. Ironically, more recent studies suggest that the capacity for ticks’ saliva to facilitate transmission could actually have applications for cancer treatment.

Who Can Take Part in the Lyme Disease Trial?

To be eligible to take part in the trial, patients must be over eighteen and have had the erythema migrans Lyme disease rash and antibiotic treatment in the past four months. Patients having had antibiotics in the last month are excluded from the study however. Those diagnosed with early or late Lyme disease, who have received antibiotics, and who still have high circulating levels of antibodies to Borrelia burgdorferi are still eligible for the study into Chronic Lyme disease, as are those treated more than three months ago who have new symptoms associated with Lyme disease more than six months after completing antibiotic therapy. Those with Lyme arthritis are also able to take part in the study as well as healthy volunteers with no history of Lyme disease infection, meaning that the families and friends of Lyme disease sufferers also have a way of helping research.

How Xenodiagnosis Works

Patients taking part in the study will have an initial physical examination, medical history and blood samples taken, prior to having their first study visit involving ticks. This will include a strip of filter paper containing twenty to thirty disease-free ticks being placed on the volunteer’s skin, at the site of a Lyme disease rash or symptomatic area where appropriate. Four to six days later, the ticks will be removed, collected, and sent for assessments. A skin biopsy will be taken from the participants, as well as another blood sample, before a final blood sample is taken a month afterwards. A list of exclusion criteria is also available and includes such things as autoimmune illness requiring aggressive treatment, pregnancy or lactation, and recent use of oral steroids.

Clinical Trial Results Anticipated

Unfortunately, the trial is to continue over three more years, with the earliest completion date at July 2015. There is hope that some preliminary results and indications will be published sooner in order to allow other researchers to consider their investigative path in the meantime. Patients previously turned down for treatment or who cannot get insurance coverage for Chronic Lyme disease treatment may see this new technique of xenodiagnosis as their last chance to prove that their symptoms and suffering are real. Just how many are willing to endure five days walking around with ticks attached to them remains to be seen.

Chronic Lyme Disease and Post-Treatment Lyme Disease Syndrome

The existence of Chronic Lyme disease has been questioned by medical authorities and remains controversial, with the term Post-Treatment Lyme Disease Syndrome preferred in orthodox medical circles. This assumes that a patient has been diagnosed with Lyme disease, has been treated with antibiotics according to current guidelines, and yet continues to have symptoms reminiscent of the infection. Antibiotic treatment is said to be effective in most cases but around 20% of patients report subsequent symptoms, either continuing after treatment or recurring at a later date. PTLDS could be due to the damage inflicted on the body during the infected period, or an effect on the immune system which leads to further damage through autoimmune attack. Nothing has been clearly demonstrated however and, with the number of infections growing each year, it is hoped that this trial into xenodiagnosis will, at the very least, offer an alternative to current inadequate Lyme disease testing.